1. Field of the Invention
The present invention relates to sputtering apparatuses used for forming metal thin films, piezoelectric thin films, dielectric thin films, and other thin films, and more specifically, the present invention relates to an in-line sputtering apparatus in which a thin film is formed while a substrate is being transferred in front of a plurality of targets.
2. Description of the Related Art
Conventionally, various kinds of sputtering apparatuses for forming various kinds of thin films such as metal thin films and piezoelectric thin films, have been proposed. Generally, the thicknesses of thin films formed by sputtering apparatuses must be uniform.
In Japanese Unexamined Patent Application Publication No. 9-125240, an example of a sputtering apparatus that controls the thickness of a thin film is disclosed. FIG. 11 is a schematic diagram of a sputtering apparatus disclosed in the JP 9-125240, and FIG. 12 is a schematic plan view for explaining a thickness distribution correcting member.
As shown in FIG. 11, a sputtering apparatus 101 includes a deposition chamber 102, in which a substrate holder 103 is disposed. A substrate 104 is fixed on a surface of the substrate holder 103.
A target 105 is arranged such that the target 105 opposes the substrate 104, and a thickness distribution correcting member 106 is disposed above the target 105.
As shown in FIG. 12 by a plan view, the thickness distribution correcting member 106 includes a pair of supporting plates 106a and 106b which are fixedly disposed. The supporting plates 106a and 106b are arranged such that the supporting plates 106a and 106b oppose each other with the target 105 disposed therebetween and extend parallel to each other. In addition, the supporting plates 106a and 106b are linked with a plurality of correcting plates 106c and 106d, respectively. The correcting plates 106c and 106d are constructed to be movable in the direction shown by the arrow in the figure.
As shown in FIG. 11, in the sputtering apparatus 101, target particles 105a are sputtered away from the target by ions A, move toward the substrate 104, and are deposited on the exposed surface of the substrate 104. Accordingly, a thin film is formed. In this case, thickness uniformity of the thin film formed on the substrate 104 depends on the flatness, attachment angles, and other characteristics of the substrate 104 and the target 105. As a result, the thickness of the thin film may not be uniform. Thus, in order to ensure thickness uniformity of the thin film, the thickness distribution correcting member 106 is used in the sputtering apparatus 101. In the thickness distribution correcting member 106, the size of the opening B surrounded by the inner ends of the correcting plates 106c attached to the supporting plate 106a and the inner ends of the correcting plates 106d attached to the supporting plate 106b is adjusted so that the thickness distribution of the thin film can be corrected. More specifically, when some of the correcting plates 106c and 106d are moved to reduce the gaps therebetween, the movement of the target particles 105a toward the substrate 104 is impeded, and the thickness of the corresponding portion of the thin film is reduced.
In the sputtering apparatus 101, when positions of the correcting plates 106c and 106d of the thickness distribution correcting member 106 are to be adjusted, the deposition chamber 102 is first vented to the atmosphere. Then, correcting plates 106c and 106d are moved and are fixed at desired positions, such that the gaps therebetween are adjusted, and the pressure in the deposition chamber 102 is reduced again.
On the other hand, an in-line sputtering apparatus including a thickness controlling plate is disclosed in Japanese Unexamined Utility Model Application Publication No. 62-162255. As shown in FIG. 13, according to JP 62-162255, a sputtering apparatus 111 includes a deposition chamber 112, in which a substrate holder 113 is disposed. A substrate 114 is fixed on the substrate holder 113. Targets 116 are disposed on an inwardly facing surface of a covering member 115, which is provided for covering the deposition chamber 112. The substrate 114 is moved along with the substrate holder 113 in the direction shown by the arrow C in the figure, so that, while the substrate 114 is being transferred in front of the targets 116, target particles continuously accumulate on the substrate 114 to form a thin film.
The sputtering apparatus 111 is provided with a thickness controlling member 117, which is schematically shown in FIG. 13. The actual shape of the thickness controlling member 117 as seen from the front is shown in FIG. 14. The thickness controlling member 117 includes a supporting plate 118 having a rectangular shape which is provided with a rectangular opening. Correcting plates 119 and 120 constructed of metal are fixed to the supporting plate 118 at two sides thereof so as to oppose each other in the lateral direction. Inner edges 119a and 120a of the correcting plates 119 and 120 oppose each other, and the shapes thereof are determined in accordance with the correction of the thickness distribution of the thin film. The shapes of the inner edges 119a and 120a of the correcting plates 119 and 120, respectively, are adjusted by cutting metal plates, and vary along the vertical direction as shown in the figure. When the substrate 114 is transferred in the direction shown by the arrow C (FIG. 13), the movement of the target particles knocked away from the target 116 is impeded by the correcting plates 119 and 120. Accordingly, the thickness distribution is corrected such that the thickness of the thin film is reduced at portions where the gap between the inward edges 119a and 120a is narrow, and is increased at portions where the gap therebetween is wide.
As described above, according to the sputtering apparatus shown in FIGS. 11 and 12, which is disclosed in Japanese Unexamined Patent Application Publication No. 9-125240, the thickness distribution is corrected by adjusting the widths of the gaps between the correcting plates 106c and 106d. However, there is a problem in that the relationship between the change of the sizes of the gaps and the change of the thickness distribution of the thin film formed is not reliable, and it is difficult to control the thickness distribution of the thin film with high accuracy.
In a sputtering process, an erosion region of the target is sputtered, and target particles are knocked away from the target and accumulated on a substrate so that a thin film is formed. The thickness of the thin film formed on the substrate varies depending on the coverage of the erosion region of the target by the correcting plates 106c and 106d. In the above-described conventional technique, although the gaps between the correcting plates 106c and 106d are adjusted, the coverage of the erosion region of the target is not determined.
Thus, as schematically shown in FIGS. 15A and 15B, the correcting plates 106c and 106d cover the erosion region of the target 105 asymmetrically. Accordingly, although the thickness of the thin film may be reduced by reducing the gaps between the correcting plates 106c and 106d, a reliable relationship between the displacements of the correcting plates 106c and 106d and the thickness variation of the thin film cannot be obtained. Thus, in order to make the thickness uniform, processes of adjusting the positions of the correcting plates 106c and 106d and measuring the thickness distribution of the formed thin film must be performed several times.
Thus, in the method according to the above-described conventional technique, only the gaps between the correcting plates 106c and 106d are adjusted, and the correcting plates 106c and 106d are not moved symmetrically about the center of the target 105 and the substrate 104.
In addition, in the method according to the above-described conventional technique, the deposition chamber 102 must be vented to the atmosphere when the positions of the correcting plates 106c and 106d are to be adjusted after having been already set. Thus, a significant amount of time is required to adjust the thickness of the thin film in the deposition process.
On the other hand, in the sputtering apparatus disclosed in Japanese Unexamined Patent Application Publication No. 62-162255, the shapes of the inner edges 119a and 120a of the correcting plates 119 and 120 are determined in accordance with targets and substrates. Thus, if the deposition process is performed and the target is changed after the correcting plates 119 and 120 are cut and the shapes of the inner edges 119a and 120a are determined, the inner edges 119a and 120a of the correcting plates 119 and 120 must be reprocessed in accordance with the new target. Since the correcting plates 119 and 120 must be reprocessed, a significant amount of time is required for correcting the thickness distribution, and high costs are incurred.
In addition, in the sputtering apparatus 111, the substrate 114 is transferred in front of the target 116. However, the substrate holder 113 may be inclined in the transfer direction (horizontal direction) or in the vertical direction. Thus, even when the thickness distribution is corrected by using the thickness controlling member 117, the distance between the substrate 114 and the target 116 is not always constant in the vertical or in the above-described transfer direction. Accordingly, even when the thickness is controlled by the thickness controlling member 117, it is difficult to form thin films having a uniform thickness with high reproducibility.
In order to overcome the problems described above, preferred embodiments of the present invention provide an inline sputtering apparatus which makes the adjusting operation for the thickness control simpler and reduces the time required therefor, and forms a thin film having a uniform thickness reliably and easily.
According to a preferred embodiment of the present invention, an in-line sputtering apparatus includes a deposition chamber, a target installed inside the deposition chamber, a substrate holder to hold a substrate, a substrate holder transferring mechanism which transfer the substrate holder relative to the target such that a thin film including a material of the target is formed on the substrate held by the substrate holder, first and second thickness distribution correcting members and the plate driving mechanism. The first and second thickness distribution correcting members are provided above the target, and each of the first and second thickness distribution correcting members has a plurality of moveable plates. The plate driving mechanism is linked to the first and second thickness distribution correcting members and symmetrically moves the corresponding moveable plates of the first and second distribution correcting plates.
The plate driving mechanism may include a control unit which is disposed outside of the deposition chamber, and a link mechanism of which one end is linked to the control unit and the other end is linked to the first and the second thickness distribution correcting members.
The substrate holder transferring mechanism may include a guide rail that is disposed in the deposition chamber and extends along the transfer direction of the substrate and along which the substrate holder is constructed to be moveable, and a driving mechanism for driving the substrate holder.
The in-line sputtering apparatus may further include an ambient gas injection pipe for injecting an ambient gas into the deposition chamber. The ambient gas injection pipe preferably includes nozzles to eject the ambient gas toward the centers of the target.
In the in-line sputtering apparatus according to various preferred embodiments of the present invention, each of the first and the second thickness distribution correcting members preferably includes a plurality of moveable plates. The moveable plates of the first and the second thickness distribution correcting members are moved in pairs symmetrically by the plate driving mechanism. Since the moveable plates are moved in pairs symmetrically, the relationship between the displacements of the moveable plates of the thickness distribution correcting members and the change of the thickness distribution is reliably obtained, and the thickness distribution is controlled with high accuracy.
Accordingly, in the in-line sputtering apparatus in which a thin film is formed on a substrate while the substrate is being transferred in front of a plurality of targets, a thin film having a uniform thickness is reliably formed, even when regional differences in thickness thereof are caused at each of the targets, by correcting the thickness distribution with the use of the first and the second thickness distribution correcting members and the plate driving mechanism.
The plate driving mechanism may include a control unit which is disposed outside of the deposition chamber and a link mechanism of which one end is linked to the control unit and the other end is linked to the first and the second thickness distribution correcting members. In such a case, the thickness distribution control using the first and the second thickness distribution correcting members is easily performed by operating the control unit which is disposed outside of the deposition chamber. Accordingly, it is not necessary to vent the deposition chamber to the atmosphere, and the operation of adjusting the thickness distribution is performed more easily.
When a guide rail is provided in the deposition chamber and a substrate holder is constructed to be moveable along the guide rail, the substrate held by the substrate holder is more reliably transferred in the transfer direction. Accordingly, differences in thicknesses between thin films formed on substrates held by different substrate holders are eliminated.
In addition, when nozzles of ambient gas injection pipes are disposed such that ambient gas is ejected toward the centers of the targets, the gas uniformly flows over the targets. Accordingly, the thickness distribution is accurately adjusted by the thickness distribution correcting members with high reproducibility.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.